Abstract: Apparatus is disclosed for aligning, i.e., de-skewing, sheet material having squared upstream and downstream edges which is being advanced along a path. The advancing apparatus includes a pair of endless belts having pushers projecting therefrom which engage the upstream edge of the sheet material to advance the sheet material with rotation of the belts. The disclosed apparatus adjusts the relative positions of the pushers so that the squared upstream and downstream edges of the sheet material are normal to the path of travel of the sheet material. The invention has particular application to mailing machines in which paper sheets to be inserted in envelopes are advanced towards a folding station and/or an envelope insertion station. The invention has particular application to use with apparatus that cross folds paper.